The present invention relates to golf balls and specifically to the construction of solid, non-wound, golf balls for regulation play. More particularly, the invention is directed to improved golf balls comprising multi-component core assemblies which have a pressurized foamed center component. The pressurized foam center is encapsulated by one or more core layers which are then surrounded by a cover. The golf balls of this invention are of the same size and weight as conventional balls and have comparable or better performance characteristics.
Golf balls traditionally have been categorized into three different groups. These are one piece balls, multi-piece solid balls comprising two or more solid pieces and wound (three piece) balls.
The one piece ball typically is formed from a solid mass of moldable material which has been cured to develop the necessary degree of hardness. In many instances, the one piece solid ball does not possess any significant difference in composition between the interior and exterior of the ball. One piece balls are described, for example, in U.S. Pat. Nos. 3,313,545; 3,373,123; and, 3,384,612.
A wound ball is frequently referred to as a xe2x80x9cthree piece ballxe2x80x9d since it is made with a vulcanized rubber thread wound under tension around a solid or semi-solid center to form a wound core and thereafter enclosed in a single or multi-layer covering of tough protective material. For many years the wound ball was desired by many skilled, low handicap golfers, due to reported enhanced playability characteristics.
More particularly, the three piece wound ball typically has a balata or balata like cover which is relatively soft and flexible. Upon impact, the balata cover compresses against the surface of the club producing high spin. Consequently, the soft and flexible balata covers, along with the wound cores, provide an experienced golfer with the ability to apply a spin to control the ball in flight. This allows a skilled golfer to produce a draw or a fade or a backspin which causes the ball to xe2x80x9cbitexe2x80x9d or stop abruptly on contact with the green. Moreover, the balata cover produces a soft xe2x80x9cfeelxe2x80x9d to the low handicap player. Such playability properties of workability, feel, etc. are particularly important in short iron play with low swing speeds and are exploited significantly by highly skilled players.
However, a three piece wound ball also has several disadvantages. For example, a wound ball is relatively difficult to manufacture due to the number of production steps required and the careful control which must be exercised in each stage of manufacture to achieve suitable roundness, velocity, rebound, xe2x80x9cclickxe2x80x9d, xe2x80x9cfeelxe2x80x9d, and the like.
Moreover, wound balls can also be knocked xe2x80x9cout of roundxe2x80x9d. One or more severe hits can damage the windings and knock the center xe2x80x9coff centerxe2x80x9d. Such a ball is then unbalanced, making putting, etc. more difficult.
Additionally, a soft wound (three piece) ball is not well suited for use by the less skilled and/or high handicap golfer who cannot intentionally control the spin of the ball. For example, the unintentional application of side spin by a less skilled golfer produces hooking or slicing. The side spin reduces the golfer""s control over the ball as well as reducing travel distance.
Similarly, despite all the benefits of balata, balata covered balls are easily cut and/or damaged if mishit. Consequently, golf balls produced with balata or balata containing cover compositions can exhibit relatively short life spans. As a result of this negative property, balata and its synthetic substitute, trans-polyisoprene, and resin blends, have been essentially replaced as the cover materials of choice by golf ball manufacturers by materials comprising ionomeric resins and other elastomers such as polyurethanes.
Conventional multi-piece solid golf balls, on the other hand, include a solid resilient core having single or multiple cover layers employing different types of material molded on the core. The one piece golf ball and the solid core for a multi-piece solid (nonwound) ball frequently are formed from a combination of materials such as polybutadiene and other rubbers cross linked with zinc diacrylate or zinc dimethacrylate, and containing fillers and curing agents which are molded under high pressure and temperature to provide a ball of suitable hardness and resilience. For multi-piece nonwound golf balls, the cover typically contains a substantial quantity of ionomeric resins that impart toughness and cut resistance to the covers.
Ionomeric resins are generally ionic copolymers of an olefin, such as ethylene, and a metal salt of a unsaturated carboxylic acid, such as acrylic acid, methacrylic acid or maleic acid. Metal ions, such as sodium or zinc, are used to neutralize some portion of the acidic group in the copolymer, resulting in a thermoplastic elastomer exhibiting enhanced properties, such as durability, for golf ball cover construction. However, some of the advantages gained in increased durability have been offset to some degree by decreases in playability. This is because, although the ionomeric resins are very durable, they also tend to be quite hard when utilized for golf ball cover construction and thus lack the degree of softness required to impart the spin necessary to control the ball in flight. Since most ionomeric resins are harder than balata, the ionomeric resin covers do not compress as much against the face of the club upon impact, thereby producing less spin. In addition, the harder and more durable ionomeric resins lack the xe2x80x9cfeelxe2x80x9d characteristic associated with the softer balata related covers.
As a result, while there are currently more than fifty (50) commercial grades of ionomers available, both from DuPont and Exxon, with a wide range of properties which vary according to the type and amount of metal ions, molecular weight, composition of the base resin (i.e. relative content of ethylene and methacrylic and/or acrylic acid groups) and additive ingredients, such as reinforcement agents, etc., a great deal of research continues in order to develop golf ball cover compositions exhibiting not only the improved impact resistance and carrying distance properties produced by the xe2x80x9chardxe2x80x9d ionomeric resins, but also the playability (i.e. xe2x80x9cspinxe2x80x9d, xe2x80x9cfeelxe2x80x9d, etc.) characteristics previously associated with the xe2x80x9csoftxe2x80x9d balata covers, properties which are still desired by the more skilled golfer.
Moreover, a number of multi-piece solid balls have also been produced to address the various needs of the golfing population. The different types of material used to formulate the core(s), cover(s), etc. of these balls dramatically alter the balls"" overall characteristics.
In this regard, various structures have been suggested using multi-layer cores and single layer covers wherein the core layers have different physical characteristics. For example, U.S. Pat. Nos. 4,714,253; 4,863,167 and 5,184,828 relate to three piece solid golf balls having improved rebound characteristics in order to increase flight distance. The ""253 patent is directed towards differences in the hardness of the layers. The ""167 patent relates to a golf ball having a center portion and an outer layer having a high specific gravity. Preferably, the outer layer is harder than the center portion. The ""828 patent suggests that the maximum hardness must be located at the interface between the core and the mantle, and the hardness must then decrease both inwardly and outwardly.
Similarly, a number of patents for multi-piece solid balls suggest improving the spin and feel by manipulating the core construction. For example, U.S. Pat. No. 4,625,964 relates to a solid golf ball having a core diameter not more than 32 mm, and an outer layer having a specific gravity lower than that of the core. In U.S. Pat. No. 4,650,193, it is suggested that a curable core elastomer be treated with a cure altering agent to soften an outer layer of the core. U.S. Pat. No. 5,002,281 is directed towards a three piece solid golf ball which has an inner core having a specific gravity greater than 1.0, but less than or equal to that of the outer shell which must be less than 1.3.
U.S. Pat. Nos. 4,848,707 and 5,072,944 disclose three-piece solid golf balls having center and outer layers of different hardness. Other examples of such dual layer cores can be found in, but are not limited to, the followings patents: U.S. Pat. Nos. 4,781,383; 4,858,924; 5,002,281; 5,048,838; 5,104,126; 5,273,286; 5,482,285 and 5,490,674. It is believed that all of these patents are directed to balls with single cover layers.
Multi-layer covers containing one or more ionomeric resins have also been formulated in an attempt to produce a golf ball having the overall distance, playability and durability characteristics desired. This was addressed in U.S. Pat. No. 4,431,193, where a multi-layered golf ball cover is described as having been produced by initially molding a first cover layer on a spherical core and then adding a second cover layer. The first or inner layer is comprised of a hard, high flexural modulus resinous material to provide a gain in coefficient of restitution while the outer layer is a comparatively soft, low flexural modulus resinous material to provide spin and control. The increase in the coefficient of restitution provides a ball which serves to attain or approach the maximum initial velocity limit of 255 feet per second, as provided by the United States Golf Association (U.S.G.A.) rules. The relatively soft, low flexural modulus outer layer provides for an advantageous xe2x80x9cfeelxe2x80x9d and playing characteristics of a balata covered golf ball.
In various attempts to produce a durable, high spin ionomeric golf ball, the golfing industry has also blended the hard ionomer resins with a number of softer ionomer resins. U.S. Pat. Nos. 4,884,814 and 5,120,791 are directed to cover compositions containing blends of hard and soft ionomeric resins. The hard copolymers typically are made from an olefin and an unsaturated carboxylic acid. The soft copolymers are generally made from an olefin, an unsaturated carboxylic acid and an acrylate ester. It has been found that golf ball covers formed from hard-soft ionomer blends tend to become scuffed more readily than covers made of hard ionomer alone.
A dual core, dual cover ball is described in U.S. Pat. No. 4,919,434. However, the patent emphasizes the hardness characteristics of all layers, particularly the requirement for a soft inner cover layer and a hard outer cover layer. With respect to the core, it requires that the layers should not differ in hardness by more than 10 percent and should be elastomeric materials having a specific deformation range under a constant load.
U.S. Pat. No. 5,104,126 attempts to concentrate the weight of the golf ball in the center core region by utilizing a metal ball as the core component. However, that patent teaches the use of a solid metal ball as the core component which provides substantially different properties than a polymeric core.
Additionally, according to the U.S.G.A., the initial velocity of the ball must not exceed 250 ft/sec. with a 2% maximum tolerance (i.e., 255 ft/sec.) when struck at a set club head speed on a U.S.G.A. machine. Furthermore, the overall distance of the ball must not exceed 280 yards with a 6% tolerance (296.8 yards) when hit with a U.S.G.A. specified driver at 160 ft/sec. (clubhead speed) at a 10 degree launch angle as tested by the U.S.G.A. Lastly, the ball must pass the U.S.G.A. administered symmetry test, i.e., fly consistently (in distance, trajectory and time of flight) regardless of how the ball is placed on the tee.
While the U.S.G.A. regulates five (5) specifications for the purposes of maintaining golf ball consistency, alternative characteristics (i.e., spin, feel, durability, distance, sound, visibility, etc.) of the ball are constantly being improved upon by golf ball manufacturers. This is accomplished by altering the type of materials utilized and/or improving construction of the balls. For example, the proper choice of the materials for the cover(s) and core(s) are important in achieving certain distance, durability and playability properties. Other important factors controlling golf ball performance include, but are not limited to, cover thickness and hardness, core stiffness (typically measured as compression), ball size and surface configuration.
Accordingly, a wide variety of golf balls have been designed and are available to suit an individual player""s game. In essence, different types of balls have been specifically designed or xe2x80x9ctailor madexe2x80x9d for high handicap versus low handicap golfers, men versus women, seniors versus juniors, etc. Moreover, improved golf balls are continually being produced by golf ball manufacturers with technological advancements in materials and manufacturing processes.
In view in part of the above information, a number of one-piece, two-piece (a solid resilient center or core with a molded cover), three-piece wound (a liquid or solid center, elastomeric winding about the center, and a molded cover), and multi-layer solid or wound golf balls have been produced to address the various needs of golfers exhibiting different skill levels. The different types of materials utilized to formulate the core(s), cover(s), etc. of these balls dramatically alter the balls"" overall characteristics.
It would be useful to develop a golf ball exhibiting an increased resilience and feel without substantially affecting the ball""s remaining characteristics. Additionally, it would also be useful to develop a golf ball with a light-weight center having the same overall weight and size as conventional golf balls.
These and other objects and features of the invention will be apparent from the following summary and description of the invention, the drawings and from the claims.
Accordingly, it is a feature of the present invention to provide a multi-piece, nonwound, solid golf ball. The core is of a multi-layer construction. It comprises a pressurized center or inner core layer which is encapsulated by an outer core layer of different material and construction. The characteristics of the core are such that the feel, compression and/or moment of inertia of the ball may be adjusted.
An additional feature of the invention is to provide a ball having a multi-layer polymeric core having a pressurized foamed center or nucleus enclosed by an outer core layer and a multi-layer cover. The ball has enhanced feel and compression properties.
Another feature of the present invention is the provision for a golf ball having a pressurized foamed inner core. The inner core component is constructed in such a manner as to incorporate many of the desirable features associated with various categories of balls traditionally employed.
A further feature of the present invention is the provision for a golf ball core structure with a foamed inner or center polymeric core and an outer polymeric core layer, with the inner core having a specific gravity that differs from that of the outer core layer.
Yet another feature is the provision for a multi-layer core having a pressurized center that is combined with a multi-layer cover wherein the outer cover layer has a lower hardness value than the inner cover layer.
A still further feature of the invention is the provision for a golf ball having a foamed center or nucleus, a high specific gravity core layer and a soft outer cover layer with good scuff resistance and cut resistance coupled with relatively high spin rates at low club head speeds.
The present invention provides in an additional aspect, a solid, nonwound golf ball. The ball comprises a pressurized, multi-core assembly that is concentrically positioned within the center of the golf ball, and a multi-layer cover assembly disposed about the multi-core assembly.
In yet another aspect, the present invention provides a golf ball comprising a pressurized foamed center core component which is concentrically disposed about a reference point located at the geometric center of the golf ball. The golf ball further comprises an outer core layer which generally surrounds and is disposed about the center core component. The golf ball further comprises a first inner cover layer disposed and positioned around the outer core layer, and a second outermost dimpled cover layer that is disposed about the first inner cover layer. Preferably, an ionomeric material is used in at least one of the cover layers.
In yet another aspect, the present invention provides a golf ball comprising a center core component that is pressurized. Preferably, the center core component is foamed and contains a plurality of interior voids or cells, which contain an effective amount of a gas such as nitrogen that is at an elevated pressure. In certain embodiments, the pressurized center core has relatively high or low densities.
In an additional aspect, the subject matter of the present invention provides a golf ball comprising a dual polymeric core and a cover. The dual core has an inner, low density, spherical center core and at least one outer core layer. A lower or higher density outer core layer is disposed about the low density spherical center or inner core layer. A cover is then molded about the dual core.
Moreover, one or more outer core layers can be disposed about the center, followed by one or more cover layers. The outer core and/or cover layers can be made lighter and/or heavier in order to produce an overall golf ball which conforms with the weight and size requirements of the U.S.G.A. This combination of weight and size displacement decreases or increases the moment of inertia and/or allows the radius of gyration of the ball to move closer to or further from the center.
The moment of inertia (i.e., xe2x80x9cMOIxe2x80x9d) of a golf ball (also known as xe2x80x9crotational inertiaxe2x80x9d) is the sum of the products formed by multiplying the mass (or sometimes the area) of each element of a figure by the square of its distance from a specified line such as the center of a golf ball. This property is directly related to the xe2x80x9cradius of gyrationxe2x80x9d of a golf ball which is the square root of the ratio of the moment of inertia of a golf ball about a given axis to its mass. It has been found that the lower the moment of inertia (or the closer the radius of gyration is to the center of the ball) the higher the spin rate is of the ball with all other properties being held equal.
In all of the above aspects, the present invention is directed, in part, to providing a pressurized center core component. This increases the resilience and feel characteristics of the ball.
The present invention is also directed to decreasing or increasing the moment of inertia of a solid, non-wound, golf ball by varying the weight arrangement and composition of the pressurized core (preferably the inner spherical center). By varying the weight, size and density of the components of the golf ball, the moment of inertia of a golf ball can be decreased or increased. Additionally, different types of matrix materials and/or cross-linking agents, or lack thereof, can be utilized in the core construction in order to produce an overall solid, non-wound, golf ball exhibiting enhanced spin and feel while maintaining resiliency and durability.
In one other further aspect, the subject matter of the present invention provides a multi-layered covered golf ball comprising a dual core and a multi-layer cover. The dual core comprises a pressurized low or high density spherical center core layer and at least one outer core layer having a similar or different density. Preferably, the spherical center has a specific gravity of from about 0.02 to about 4.0, preferably about 0.10 to 2.0, and most preferably, about 0.30-1.0. The spherical center has a diameter from 0.15 inches to 1.0 inches, preferably about 0.25 inches to 0.75 inches and most preferably 0.0340 inches to 0.344 inches.
The golf balls of the present inventions having the foamed, pressurized nucleus are more durable and softer with an increased resilience than solid metal nucleus balls. The specific gravity of the center, or nucleus, is dependent upon the extent of foaming or cell size, the quantity and type of the material in nucleus, the amount and type of blowing agent, and the specific gravity of the chosen filler (if desired) so that the maximum U.S.G.A. golf ball weight is not exceeded.
These and other objects and features of the invention will be apparent from the following description and from the claims.